1. Field of the Invention
The present invention related to a closed evaporative cooling system for an engine, comprising a condenser for condensing vapor generated in the water jacket of the engine and introduced in the condenser tubes therefrom, by means of heat exchange between the atmosphere and vapor passing in the condenser tubes.
2. Description of the Related Art
It is known that a closed evaporative cooling system, in which cooling water is evaporated in a water jacket and the vapor is introduced in condenser tubes to be condensed therein, is more advantageous than a circulation cooling system in saving the amount of cooling water by the function of the latent heat of evaporization.
However, the former is disadvantageous in loss of water when the cooling efficiency is low.
In order to reduce the loss of water, an improved closed evaporative cooling system for a small horizontal engine disclosed in Japanese Utility Model Publication No. 44-28,022 comprises an auxiliary tank disposed at one side of a condenser, and a pipe communicating the auxiliary tank with an upper tank of the condenser, and a pressure valve fixed at the upper part of the auxiliary tank, so as to cool and condense vapor from the upper tank in the pipe, and to reserve condensed water in the auxiliary tank.
The improved system described above may reduce the loss of cooling water as a whole. However, it implies that cooling water will be transfused to the auxiliary tank and decreasing the water in the water jacket for sufficient cooling after a long running of the engine. And the temperature, at which vapor begins to condense in condenser tubes, is depressed by the depression of the internal pressure of the upper tank as a result of the condensation of vapor in the pipe communicating between the two tanks. As a result of depression of the condensation point and internal pressure in the upper tank, vapor begins to condense at the higher position in condenser tubes, and condensed water begins to fall along the internal surface of the tubes. The volume of condensed water in each tube increases as soon as the condensed water begins to fall along the internal periphery of each tube by adsorbing dewdrops of vapor rising therethrough successively, and condensed water closes the internal passages of the tubes at their higher position. Thus, water condensed in the tubes may be easily and frequently spit into the upper tank by the pressure of vapor in the water jacket, accompanying small and shocking pulsation of pressure, and the brazed or soldered part between the upper end of each tube and the lower wall of the upper tank is repeatedly and alternatively expanded by heat of vapor and contracted by coolness of water spit therethrough, in such high frequency as three times per a minute, for example. Due to the alternation of expansion and contraction, an alternative thermal stress acts on the brazed or soldered part to bring on the fracture thereof from fatigue of brazing or soldering materials.